In general, an overlay network is a network built on top of another, underlying, network. Nodes in the overlay network are interconnected by virtual or logical links, each of which corresponds to a path comprising one or more physical links in the underlying network. Distributed systems such as cloud computing networks and peer-to-peer networks are overlay networks because their nodes run on top of the Internet. Overlay networks in general, and Internet protocol (“IP”) overlay networks in particular, are gaining popularity for providing virtual machine (“VM”) mobility over layer 3 (“L3”) networks, such as Virtual Extensible Local Area Networks (“VXLANs”) and Network Virtualization using Generic Routing Encapsulation (“NVGRE”)-based networks, for example. In such overlay networks, inner layer 2 (“L2”) or L3 frames are encapsulated within an outer IP overlay encapsulation. Overlay encapsulation may begin on a virtual switch (“vSwitch”) executing within a hypervisor of a virtualized host server. In some instances, the hypervisor may be connected to two nodes, or routers, in accordance with Virtual PortChannel (“vPC”) technology. vPC enables links that are physically connected to two different nodes, referred to as “vPC peers,” to appear as a single PortChannel to the overlay network.
One common practice for distributing multi-destination traffic in an overlay network is to use multicast encapsulation on the outer header, with a vSwitch, which may be implemented as a VXLAN Tunnel End Point (“VTEP”), sending an Internet Group Management Protocol (“IGMP”) “join” message toward the overlay network via one of the vPC peers without participating in the network multicast routing protocol (which may be, for example, Protocol Independent Multicast (“PIM”)). Hypervisors, in such topologies can dually actively connecting into the fabric via a port channel, the term used as virtualPortChannel (or vPC) here. When hypervisors are dually connected, multi-destination traffic originated by VTEP (on hypervisor) may be sent back to the hypervisor by the other vPC peer; that is, the vPC peer that did not inject the traffic into the overlay network.